You could give people a mild shock. "Here. Hold these while I crank this thingy." Could be good for some lulz. Or get you burned as a witch.

Making an "ouch" device or basic heater is something I could do.

Even a battery I could make a simple alumium air battery cell. Or lemon battery. But I'd be viewed like a sorcerer asking for foreign ingredients like salt, aluminum, copper and zinc.

Joe Rogan had a good line back before he became... whatever he is now. Anyways, the line is "if I dropped you off on a deserted island, how long before you could send me an email?"

You can make a generator.. so then stretch wires to a distance and put a motor on the end of it (similar to the generator). Basically blow their minds in that you could transfer power over distance without a mechanical coupling.